VIENNA -- For the first time, a microbicide gel -- intended to be used by women during sex -- has been shown to help prevent HIV infection.

Action Points

Explain to interested patients that a microbicide vaginal gel used during sex is thought to be a key element of HIV prevention is many parts of the world, but has been elusive.

Note that this study found that such a gel, which contains the anti-HIV drug tenofovir had a significant protective effect.

VIENNA -- For the first time, a microbicide gel -- intended to be used by women during sex -- has been shown to help prevent HIV infection.

In a randomized controlled trial, a gel containing the nucleotide analogue reverse transcriptase inhibitor tenofovir (Viread) reduced the risk of women acquiring HIV by 39% compared with a placebo gel, according to Quarraisha Abdool Karim, PhD, of the Centre for the AIDS Program of Research in South Africa (CAPRISA) in Durban.

But the risk was reduced even further -- by 54% -- among women who used the gel more than 80% of the times they had sex, Abdool Karim said at the International AIDS Conference here and in a paper published online in Science.

That figure is comparable to the 57% reduction in risk seen in three major clinical trials that tested the effect of male circumcision, and even the overall benefit of 39% is higher than the 31% risk reduction reported last year to be associated with an HIV vaccine candidate. (See HIV Vaccine Reduces Infection Risk)

The finding comes after years of failed efforts to create a vaginal gel that can block HIV -- something that's regarded as an important preventive tool in places where women do not have the social power to insist on condom use.

It is not the end of the search, but it is the "end of the beginning," said Mitchell Warren, executive director of the New York-based AIDS Vaccine Advocacy Coalition.

Warren told MedPage Today that the overall size of the protective effect is probably not enough to put a product forward for licensing and general use, but it is enough to show that a microbicide gel can be made to work.

At the same time, the topical gel was safe, they found, with the overall rate and type of adverse events comparable between the arms, although those using the tenofovir gel had a significantly increased incidence (at P=0.015) of mild, self-limiting diarrhea.

The findings come from the so-called CAPRISA 004 trial, which enrolled 889 South African women, ages 18 to 40, who were HIV-negative, sexually active, and at high risk of becoming infected with the virus.

About half (445) were given vaginal applicators containing a 1% concentration of tenofovir gel, and the remaining 444 got an identical-appearing placebo gel.

The researchers assessed the participants' HIV status, sexual behavior, and gel and condom use every month for 30 months, and also recorded adverse events.

They found:

There were 38 new cases of HIV in the tenofovir gel arm, yielding a rate of 5.6 per 100 woman-years.

And there were 60 new cases in the placebo arm, yielding a rate of 9.1 per 100 woman-years.

Overall, the incidence rate ratio was 0.61, which was significant at P=0.017.

In women who used the gel more than 80% of the time, the incidence rate ratio was 0.46, which was significant at P=0.025.

Among women in the tenofovir arm who acquired the virus, there was no resistance to the drug.

Importantly, there was no renal toxicity, which had been thought to be a possible complication of the drug.

The researchers cautioned that the study is small and intended to provide a proof of concept, so that the results are not widely generalizable. Also, they noted, the study "needed to attain higher and sustained levels of adherence."

Indeed, Warren told MedPage Today, that's one of the questions that will have to be answered as researchers try to build on the study -- why did some women use the gel regularly while others did not?

Equally, he said, it will be important to find out how well women will adhere to gel use outside of the confines of a clinical trial, where they were monitored every month.

Other questions include whether different delivery methods will work as well or better and whether combinations of drugs might give more powerful protection, Warren said.

Meanwhile, U.S. officials weighed in, calling the results a "significant milestone" and an "exciting step forward."

Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said in a statement that antiretroviral drugs have been used for years to treat the virus. "We now have proof that an antiretroviral drug, in this case tenofovir, can be formulated into a vaginal gel that can protect women against HIV infection," Fauci said.

He added that the so-called VOICE study, sponsored by his institute and started last fall, is expected to enroll some 5,000 women in four African countries to test a similar microbicide, as well as oral drugs for what is called pre-exposure prophylaxis.

Kevin Fenton, MD, PhD, director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, said the results need to be confirmed, but "they suggest that we could soon have a new method to help reduce the heavy toll of HIV among women around the world."

Fenton noted in a statement that women represent the majority of new cases of HIV around the world.

"While there is clearly more work to be done in our search for new prevention methods," he said, the study shows "we are on the right track."

This article was developed in collaboration with ABC News.

The study had support from the US Agency for International Development and from TIA, a biotechnology agency of the South African government's Department of Science and Technology. Also, Gilead Sciences provided tenofovir for the manufacture of the gel used in the study.

Abdool Karim is the co-principal investigator of the HPTN Prevention Leadership Group, but reported no financial links with industry.

Accessibility Statement

At MedPage Today, we are committed to ensuring that individuals with disabilities can access all of the content offered by MedPage Today through our website and other properties. If you are having trouble accessing www.medpagetoday.com, MedPageToday's mobile apps, please email legal@ziffdavis.com for assistance. Please put "ADA Inquiry" in the subject line of your email.